#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<vector>
using namespace std;
class Solution {
public:
    int jumpFloorII(int number)
    {
        if (number <= 0)   return 0;
        if (number == 1)   return 1;
        return 2 * jumpFloorII(number - 1);

    }
};